Rotary hearth furnace provided with a removable sector for hearth maintainance



Jan. 6, 1959 c. MONTAGNA 2,867,428

ROTARY HEARTH FURNACE PROVIDED wxm A REMOVABLE SECTOR FOR HEARTHMAINTAINANCE Filed Aug. 4, 1955 United States Patent ROTARY I-IEARTHFURNACE PROVIDED WITH A REMOVABLE SECTOR FOR HEARTH MAIN- TAINAN CECarlo Montagna, Dalmine, Italy, assignor to Dalmine S. p. A., Milan,Italy, a corporation of Italy Application August 4, 1955, Serial No.526,492 Claims priority, application Italy August 10, 1954 4 Claims.(Cl. 263-7) tact as much as possible restricted. For this purpose, the

hearth is provided with raised rails or. ribs on which the objects rest,whereby the contact area between hearth and material is greatly reducedthereby causing a good heating action even at the lower portion of theindividual object.

The hearth has generally an annular shape and rotates at a moderatespeed (for instance one complete revolution around its vertical axis)taking several hours.

The rails of the hearth are constituted of one or more continuousannular ribs, co-axial with the hearthand so spaced as to permit theobjects to be heated to rest thereon only at two points (for instance,rolling mill ingots). The rails are made of refractory material and, onaccount of the continuous mechanical and thermic stresses to which theyare subjected, they have usually a short life and it is frequentlynecessary to rapidly repair them in order to maintain a proper heatingeffect on the material.

In ordinary furnaces, however, it is not possible to do any repairingwithout entering the furnace, which, in turn, cannot be done withoutextinguishing the fire therein; in practice it follows from this, giventhe short life of the rails and in view of economical considerationswhich exclude frequently stopping the furnace, that the latter isusually operated without rails all the time.

These difliculties and drawbacks are obviated by the hearth according tothe present invention, substantially characterized by the fact that theannular arch and walls of the furnace, along a sector-shaped portion ofthe zone located between the material charging and the discharging doorsare interrupted, While two angularly spaced, radially extending verticalend walls having each an opening for the passage of the hearth includingits rails, permit the latter to be fully accessible in its uncoveredportion between said end walls, thus permitting operations ofmaintenance to be carried out on the hearth itself from the outside ofthe furnace in said uncovered area.

The invention will be described with reference to the accompanyingdrawing, description and drawing being given by way of example only,without limiting the scope of the invention.

Fig. 1 is a diagrammatic perspective view of the uncovered hearth zoneof a furnace according to the invention.

Fig. 2 is a perspective view of the closing cover.

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The stationary arched part A of the furnace is annular in form andinside it rotates the annular hearth B in the direction of the arrow X.By C and D are respectively indicated the charging and dischargingdoors.

As stated, the hearth is provided with two or more continuous annularrelief ridges or rails Bland B2 on which the material to be treated isplaced.

The annular body of the arch of its furnace A and the walls down to thelevel of the hearth B, are interrupted within the area of the sectorlocated between the access doors C and D of the furnace, i. e., in theportion in which the hearth is not carrying any material. Two verticalwalls or ends A1 and A2 terminate the furnaces stationary part thusdefining and bounding the open sector and keeping the heating chamberclosed against the surrounding air. The walls A1 and A2 are provided intheir lower part with an aperture having its edges somewhat spaced fromthe hearth B and thereby permitting the free movement of the latter.

When the rails B1 and B2 do not require any repair, the portion of thehearth located between the two walls A1 and A2 is conveniently coveredwith a bridge shaped cover E that fits between the walls A1 and A2 andprevents the hearth from coming in contact with the outside air andcooling off. The cover E, whose location, when put in place, isindicated by dash-dot lines in Fig. 1 may, for instance, be made ofrefractory material.

The cover E can, of course, instead of being one integral piece also bemade up of several adjacent smaller sectors.

When the hearth is to undergo repairs, the cover E is removed so as touncover the hearth B. Should the repair be one of short duration thefurnace is not stopped since the time within which the portion to berepaired travels through the uncovered sector of the stationary part, ofthe furnace is generally sufficient for the repair work. Should moresubstantial repairs have to be made,

the hearth is stopped while leaving the fire burning and the rails B1and B2 are repaired or wholly substituted as far as accessible in theuncovered part of the hearth. The hearth is then put in motion againuntil the repaired portion has disappeared through the opening in wallAl, so that a following or other portion to be repaired becomesaccessible in the open sector during a new stop of the hearths rotation.The operation can be repeated until the entire repairs or substitutionof the rails is completed, after which, the cover E having beenreplaced, the furnace can begin again to run under normal operationalconditions.

It is therefore possible to carry-out repairs with the described furnacewhile it is in operation without discharging the material and even toentirely substitute the rails without stopping the hearth for any lengthof time that would be inconvenient or detrimental.

In practice the details of the furnace may be varied without departingfrom the gist and scope of the invention as claimed.

I claim:

1. A rotary hearth furnace comprising, in combination, housing meansincluding an annular base portion and an arcuate hollow upper portion onsaid annular base portion, said upper portion having a pair of radiallybase portion and said upper portion and adapted to rotate along saidbase portion, said annular hearth means passing through said passageopenings of said transverse end walls so that a portion of said annularhearth means is accessible from outside said housing means; andremovable cover means fitting between saidtransverseend walls forcovering said annular hearth means between said transverse end wallswhereby said annular hearth means may be completely enclosed when accessto said portion thereof is not desired.

2. A rotary hearth furnace comprising, in combination, housing meansincluding an annular base portion and an arcuate hollow upper portion onsaid annular base portion, said upper portion having a pair oftransverse end walls, each of said end walls being formed with a passageopening, said housing means being formed with a radially directedcharging opening adjacent one of said end walls and with a radiallydirected discharging opening adjacent the other of said end walls;movable door means on said housing for covering and uncovering saidcharging and discharging openings thereof; annular 2 hearth meanslocated intermediate said base portion and said upper portion andadapted to rotate along said base portion, said annular hearth meanspassing through said passage openings of said transverse end walls sothat a portion of said annular hearth means is accessible from outsidesaid housing means, said annular hearth means including rail meansthereon adapted to hold an object to be treated by said furnace andpassing through said passage openings of said transverse end walls sothat a portion of said rail means is accessible from outside the housingmeans for-repair or replacement procedures; and removable cover meansfitting between said transverse end walls for covering said annularhearth means between said transverse end walls whereby said annularhearth means maybe completely enclosed when access to said portionthereof and of said rail means is not desired.

3. A rotary hearth furnace as set forth in claim 1 wherein said passageopenings in said end walls are of a predetermined height and width, andwherein said annular hearth means project from said base portion with across-section substantially equal to said height and-width of saidpassage openings, so that said hearth means can pass through saidpassage openings with a minimum of air gapbetween one and the other, andwherein the inside dimensions of said removable cover means aresubstantially the same as those of said passage openings.

4. A rotary hearth furnace as set forth in claim 2 wherein said passageOpenings in said end walls are of a predetermined height and width, andwherein said annular hearth means project from said base portion with across-section substantially. equal to said height and width of saidpassage openings, so that said hearth means can pass through saidpassage openings witha minimum of air gap between one and the other, andwherein the inside dimensions of said removable cover means aresubstantially the same as those of said passage openings.

References Cited in the file of this patent UNITED STATES PATENTS693,062 Potter Feb. 11, 1902 699,528 Hunt et a1 May 6, 1902 700,427Keyes May 20, 1902 1,362,296 Hagan et al. Dec. 14, 1920 2,499,926 LloydMar. 7, :1950 2,622,861 Talley Dec. 23, 1952

